Method of and apparatus for grinding commutator brushes



Jan. 11 1927.

H. A. LEWIS METHOD OF AND APPARATUS FOR GRINDING GOMMUTA'IOR BRUSHES 3 Sheets-Sheet 1 Filed Oct. 31. 1924 Illl'lll Jan. 11 1927. H A LEWIS.

METHOD OF AND APPARATUS FOR GRINDING COMMUTATOR BRUSHES I ull xll wmw m Q R m mll l $1 m w Jill}. 11.5%. 2

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H. A. LEWIS METHOD OF AND APPARATUS FOR GRIIiDING COMMUTATOR BRUSHES Filed Oct. 31 1924 3 Sheets-Sheet 5 INVENTOR Fatented Jan. 11, 1927..

UNITED STATES PATENT 'orrica.

HARRY A. LE'W IS, OF NORRIS'IOWN PENNSYLVANIA.

Application filed October 31, 1324. Serial No. 747,042.

My invention relates to a method of and apparatus for grinding commutator brushes and'the like, and more particularly to a method and means whereby the contacting surfaces of the brushes may be ground to the curvature of different sizes of commutators, and whereby the body of the article may have the. proper angularity with respect to the said contacting surfaces.

Heretofore it has been the usual practice to effect proper contact between a commutator brush and its commutator'b'y interposing a sheet of sand paperor the like between the brush and the commutator, or by simply placing a brush in operative position and permitting it to wear to the proper contour. Both these methods are unsatisfactory because, in the first place, the operation is slow and tediousandparticles of abrasive become lodged in theinsulation and the brush is usually not closely shaped to the contour of the armature until after ithas been in use for some time. In the second instance, where the brush is shaped through contact with the commutator, a great deal of sparking occurs and a considerable deposit of particles from the brush during the early stage of grinding finds its way into the crevices of the commutator.

My invention has for one of its objects the provision of a means and a method whereby the brushes may be conveniently and accurately formed to fit commutators of dif'ferent diameters, before placing them in operative position. I

Another object of my invention resides in the provision of a means and a method whereby accurate measurements of the commutator and the angularity. of the brush with respect thereto may be obtained, and the measurements utilized in adjusting a machine for grinding the brushes.

Still another object of my invention is to provide a grinding machine for commutator brushes, of improved form.

Some of the forms which my invention may take are shown in the accompanying drawings, wherein Fig.1 is a view' of a grinding machine embodying my invention, in side elevation; Fig. 2 is a plan view thereof; Fig. 3 is anelevational view looking from the left-of Fig. 1; Figs. 4 and 5 are side elevational and plan views, respectively, of amodified form of grinding machine; Fig- 6 is a View showing a tool employed for that is driven from the motor 20 measuring the curvature of a commutator and the angularity of the brush with respect thereto; and Fig. 7 is a View showing a scale whereby a reading of the results obtained as shown in Fig. 6 may be secured.

Vhile I herein Show and describe my invention as employed in connection with the shaping of commutator brushes, it will be apparent that it may be useful in other relations.

Referring now to Figs. 1 to 3, 8 indicates the fixed base of a machine upon which a bearing structure 9 may be mounted for adjustment longitudinally of the base, by

means of bolts 10 carried by the support 9 and having their shanks and heads fitting within T-slots in the base 8. A carriage 11 is pivotally mounted upon the support 9 through the medium of a pair of bearings 12 of a slide 14.

The carriage 11 is provided upon its lower surface with a pair of ribs 13 of dove-tail form that mesh with grooves in the slide 14. The carriage is movable longitudinally of the slide by means of a screw 15 which is rotatably mounted in bearings 16 that project downwardly from the carriage 11. The screw 15 is rotated by a handle 17 and has threaded engagement wit-h a nut 18 which is secured to the underside of the slide 14.

The screw 15 is held against longitudinal movement with respect to the bearings 16, so

that as it is rotated the carriage 11 will be moved longitudinally of the bed 8. 7

Upon the forward end of the carriage 11 I provide an extension 19 for supporting an electric motor 20 and a grinding wheel 21 through the medium of a belt22. The carriage 11 is rotatable about the bearings 12 by means of 'a screw 23 that is provided with ahandle24; The screw has threaded engagement with a nut 24 that is pivotally mounted and that has a bearing pin25 projectingtherefrom as shown in Fig. 3, and is thereby pivotally supported in a boss or bearing block 26 projecting upwardly fromthe base 8.'The shank of the screw 23 passes through a bearing 27 With which it is rotatably associated, but wherein it is held against longitudinal movement. The bearing 27 is pivotally supported by the slide 14 in, a manner similar to the support the nut 24. I from the foregoing it will be seen that, the

grinder is adjustable in two directions, (a) through an are about the pivots'lQ, and (7)) in a direction longitudinally of the base 8. This latter adjustment is normallyefi ected by means of the screw 15, but for wider ranges of adjustment the bolts 10 may be loosened and the bearing block 9 slid along the base 8.

The grinder 21 is mountedfor operation upon a carbon block or brush 27 which may be mounted in a holder 28, the block or brush 27 being clamped in position therein by means of a screw 29. The holder 28 is mov able vertically by a screw 30 which engages a nut 31 carried by the holder 28, and is rotatably supported but held against longitudinal movement, by a bracket 32. The bracket 32 is slidably supported upon a block 33. by means of a screw 34: that is rotatable in the block and hasthreaded engagement with a nut. 35 which is secured to the bracket 32.

The block is pivotally mounted at 36 upon the base 8 and is adjustable about said pivot by means of a clamping bolt 37 carried by the block and an arcuate slot 38 provided in the base.

By reason of the formand arrangement of the supporting structure just reterred to. the brush QTmay be moved to various positions with respect to the grinder 21. For instance, the block 33 may be adjusted about its pivot 36 to vary the angle of the brush with respect to the grinder 21, in a radial direc tion. The bracketed). may be adju .ed toward and from the grinder 21 to eiiect the proper depth of cut and the holder 28 may be adjusted vertically to etlect the broper angularity of cut across the "front ot the brush.

' When the brush has been given the desired adjustment with respect to the grii'ider, the motor 20 may be operated to rotate the grinder and the grinder caused to. move across the face of the brush by operating the screw 23 to oscillate the carriage 11 about its pivots 12.

Referring now to Figs; 4 and ,5, I show a grinding machine of different form than that just described.

base a1. up ust ably mount are secured.- to

base-41. At its upper end the standard. 4:2 is provided-with a bearing blocl: which is piyotally supported by, meansot a pin L6. The block. 45 is slotted 'at n to receive a bracket arm 47 that may be adjustably posi tioned therein by means eta set screw- L8. At itsgouter end, the arm. 47 supports a bracket 4-9 that carries a brush holder 50 which is vertically adjustable therein in a manner similar to the holder 28 in the bracket 32. A brush 2'? is mounted in the holder 50. The bracket a9 is adjustably mounted upon a slide block 51 that is inturn adjustable about a pivot 5:2.

It will be seen that the arm 47 corresponds in some respects to the carriage 11 0t Fig.1, but thatI have. mounted the brush or carbon block on said arm instead of mounting the grinder and motor thereon.

The grinder 53 is mounted upon an upright 54.- that is rigidly secured. to the base ll andis driven by a belt 55 from any desired source of power.

In Fig. the-adj'ustn'ients of. thebrush 2'? with respect to the grinder are etl'ected in substantially the same manneras in the case of. Fig. 1, but instead of moving the grinderv bodily with respect to the brush. I movethe brush and permit the axis-of the grinder to remainstationary. This movement of the brush is effected by means of ascrew 56 whose lower endis rotatably supported in a bearing 57 but held against longitudinal movement therein; that ,is secured to thebase -11. Thescrew Stiengages with a nut 58 that is pivotally mounted upon the arm 4:7. The mounting of the bearing 57, and the nut 58 may be similar to the mounting of themembersQet and 27 in Fig.

The arm l? is not. intended to be movable longitudinally. but the. standard 42 is moyable along the base. tlto. changethe location of the pivotal. point 4L6 longitudinally of the arm, thus Va ying theraoins ot'. the curve in which the brush 2? will .move when the arm is oscillated by the screw 56.

In Figs. 6 and 7.1 showineans whereby a radial measurement may be obtained to serve as a guide for eliecting the adjustment the arms 11 ort7 withii'espect to their pivots, to provide the desired varc ofmovement between the brush holder and! the grinder.

1nv Fig. 6. 61 representsa commutator, 62 a measuring instrument provided with proections Gel; and with a hole for; the reception of a pin .65:that maybe positioned therein bya set screw 66.. A. plate 67 is pivotally mountednpon the instrument 62. I

In order to determine the curvatureot the commutator. the instrument 62is placed thereagainst, with the members 64 in en gageinent therewith, and the endof the pin-.65 is al-ov brought into. engagement with the periphery of thecommutator. The plate 67.is then laid against the side ofthe brush 2 7:to measurethe angularity thereof; hen the ineasiireliients have'been thus secured the tool. 62 is placedupon a chart as shown in Fig. 7. Tlielinner end, of the projections 6-l andthe pin 65 areplaced adjacentto the curve with which they most nearly coincide. The radius otthese curves is indicatedv in inches and fractions of inches, as shown. The angularity of the plate 67, and henceot the brush, is determined by the radial lines Ill) brush, and the bracketr are marked to indicate degrees. For instance. if it is desired to duplicate the brush of Fig. 6, the measuring instrument applied to the commutator (31 in the manner show and caused to engage with the brush. The positions or" the movable parts and ($7 of the measuring instrument 62 are maintained and such instrument applied to the chart of Fig. 7. In the instance shown, the commutator is indicated as having a radius of 2 and the brush as having an angle of 25.

\Vith the readings thus provided through application of the tool to the chart of Fig. 7, the position of the grinder 21 with respect to its pivot 12 is so adjusted that the face of the grinder will move in an are two inches radially distant from the pivot 12, and therefore corresponding to the curvature of the commutator 61, in order to grind a curved contactingsurface on the brush 27 that will accurately fit the commutator. Sim-- ilarly, the brush holder 28 may be adjusted vertically in order that the curve ground therein will be properly disposed with respect to the longitudinal center line ofthe 82 may be tilted about the pivot 36 to an angle corresponding with the 25 angle of the plate 67.

A similar procedure will be followed in the case of the machine in Figs. 4 and 5, except that the radial position of the brush with respect to its pivot 46 will be adjusted, since in that structure the grinder is mounted upon a fixed axis.

Various changes in detail and general arrangement may be made Without departing from the spirit and scope of the invention a defined in the accompanying claims.

I claim as my'invention:

l. The method of grinding commutator Yrushes. which comprises providing a grinder holder and a brush holder, one of which is pivotally mounted, that are a11gularly adjustable with respect to one another, ascertaining the desired angular position o'l the brush with respect to the commutator and the curvature of the commutator, adjusting the relative angular positions of said holders to correspond with the first-named angular position, and adjusting the position of the pivotally mounted holder radially of its pivot to correspond with the curvature desired on the contacting face of the brush, and imparting relative movement to said holder to grind the brush.

2. Apparatus for grinding commutator brushes and the like, comprising a cutting tool holder, a brusn.l1older, means for moving said tool holder through an arouate path,

means for adjusting the position of said holder radially of its pivot, a brushholder for supporting a brush in position for endwise engagement with said tool, and means for adjusting said brush holder tangentially of the path of pivotal movement of said tool. V

8. Apparatus for grinding commutator brushes and the like, comprising a cutting tool holder, a brush holder, means for moving said tool holder through an arcu-ate path, means for adjusting the position of said holder radially of its pivot, a brush holder for supporting a brush in position for endwise engagement with said tool, means for adjusting said brush holder tangentially of the path of pivotal movement of said tool, and means for adjustably positioning the brush holder about an axis that is parallel to the axis ofmovement of the tool holder.

In testimony whereof I, the said HARRY A. Lewis, have hereunto set my hand.

HARRY A. LEWIS. 

